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Library of Alexandria: Fact vs Theory vs Law vs Hypothesis vs Proof

January 30, 2013

Fact vs Theory vs Law vs Hypothesis vs Proof

There is a reasonable amount of jargon across all scientific disciplines and it is absolutely not surprising that the general public does not keep up to date on all of them, nor should they be expected to.  That being said, there are a number of scientific terms that are fairly regularly and consistently misused by the general public and the media that are fundamental to science across all disciplines.

First, lets take a look at what science actually is. According to Wikipedia: "science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe". That is pretty straightforward.  Science is a framework, or a methodology, for looking at the world around us and putting forth our best efforts to understand this crazy universe we find ourselves in. This framework can be laid out in a few simple steps outlined in this nifty little flow chart:

That is all there is to it.  That is science.  The tricky bits fall within the background research, constructing a hypothesis, designing and implementing an experiment, and analyzing the results. The finer details of these steps may vary from field to field but this is, in essence, what has taken us from tribal nomadic civilization to dropping probes on Mars.  Needless to say, it works pretty well.

Now lets dive into the headline of the article. The words listed in the title, fact, theory, law, hypothesis, and proof are words that find themselves with slightly different meanings in the common vernacular when compared to how they are used within the context of science.  This leads to much confusion in science reporting and in communicating science to the general public.  Please, please, please, keep in mind that when you are reading and listening to scientific discussion of any kind these words must be understood within the proper context and not as they are typically used by the general public in day to day conversation.

Scientific Hypothesis: A scientific hypothesis is a testable explanation about some phenomenon. This could range from an explanation as to why apples fall from trees to why homo-sapiens walk on upright on two legs and well beyond. As long as it attempts to explain something and it is testable it is a scientific hypothesis. There are good and bad hypotheses and the quality of ones hypothesis is likely going to be intricately connected to the original question and the quality and extensiveness of the background research and relevant background knowledge of the individual generating the hypotheis. The key difference between a hypothesis as used in day to day discord and a scientific hypothesis is that a scientific hypothesis is necessarily testable. Hypothesis testing is a whole other issue that I may tackle in the future but for now lets leave it at that.

Scientific Fact: A fact, within the context of science, is very basic.  A scientific fact is in essence an objective and verifiable observation. It is a fact that when standing on the surface of earth if one were to release an object from their outstretched hand that the released object will fall towards the ground. This is an objective reality that anyone can go and test at any time. Facts are collected when we repeatedly fail to reject a hypothesis during experimental testing.

Scientific Theory: Here comes one of the big problems. In general conversation when someone uses the word theory they are using the word the same way a scientist might use hypothesis. The person most likely means that they have some kind of guess or hunch.  When a scientist uses the worth theory they mean something entirely different.  Within the context of science a theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Further, a scientific theory must be able to be used to make predictions about natural events and phenomena that are consistently accurate. A simple way of thinking about a theory is that is is what we use to explain the facts we observe in the world. Sticking with the gravitation example given above the Theory of Gravity is not a guess or a hunch about gravity.  The theory of gravity is an attempt to explain how and why when you release that object from your hand it falls.

Scientific Law: While a scientific theory may help us to explain the world around us a scientific law is something entirely different.  A law, within the context of science, is a statement that is based on repeated experimental observation that describes some aspect of natural phenomenon. While the theory of gravity may strive to explain why things fall when you release them the a law of gravity will describe the falling.  As such, laws are often expressed using mathematics. It should be noted that a theory can never be "upgraded" to a law as they are completely different things.

Proof: This is important. Outside the world of mathematics, science does not and cannot "prove" anything. That is simply not how it works. Continued use of the scientific method builds supporting evidence or refuting evidence for existing theories and laws and is used in the construction of new theories and laws.  That is all there is. If you were reading closely earlier you may have noticed a curious way of describing the outcome of an experiment. "Facts are collected when we fail to reject a hypothesis during experimental testing".  This is significant and important to understand. An experiment in science does not prove the hypothesis, is either rejects the hypothesis or fails to reject it.  We are inherently incapable of  designing and carrying out an experiment 100% perfectly. Because of this we can never know with certainty that the outcome was not caused by some unaccounted for variable, some bias, or some mistake.  Instead, we slowly chip away at the unknown by demonstrating what is not and raising up what is left for further criticism and refinement.

I hope this brings some clarity to the discussion of science and that those who stumble across this find it interesting and useful. 



At May 2, 2013 at 12:11 PM , Blogger TheMoreTheWonderGrew said...

If we want more acceptance by lay people, we probably need to adapt, and dispense with the word 'theory'. We need a word that has a lay implication of the 'current view of', or 'framework for', and not the lay implication of 'hypothesis'.

At May 2, 2013 at 2:02 PM , Blogger Todd Brown said...

That would probably be a good idea. I have more interest in science than the average person, but I didn't understand the actual difference until reading this article.

At May 2, 2013 at 2:18 PM , Blogger Daniel Kroner said...

Todd, I am very pleased that you found the article educational!

Please consider checking out some of my other articles as well as following on twitter/facebook/google+ if you would like!

At May 2, 2013 at 3:42 PM , Blogger Terry A. Davis said...

If aliens sent a message 5 years ago, would that be a fact?

At May 2, 2013 at 7:21 PM , Blogger mike lurkface said...

So.. If a hypothesis is a testable explanation, and a theory is an explanation which has been tested- wouldn't that make a hypothesis the same thing as a theory?

At May 2, 2013 at 7:22 PM , Blogger mike lurkface said...

So.. If a hypothesis is a testable explanation, and a theory is an explanation which has been tested- wouldn't that make a hypothesis the same thing as a theory?

At May 2, 2013 at 9:07 PM , Blogger Evi1M4chine said...

You have a huge error in there:

If you know any of relativity, your senses, or neurology, you should know (and I think you do) that there is no such thing as “objectivity”. Every perception and every action is always subjective, and we have to live with that. Hence there is no such thing as “facts”. It’s unscientific nonsense spread by pseudo-scientists and half-knowing laymen.

Your gravity example is nice, because it so clearly shows the fallacy: Remember that recent article in science magazine about how they right now test if anti-matter reacts to gravity the same, or maybe even opposite? Well… we simply don’t know. But if that ball would be made of anti-matter, and it turns out anti-matter falls differently, your “fact” would fall apart.

Simply because there is no such thing as objectivity!

At May 2, 2013 at 9:10 PM , Blogger Evi1M4chine said...

Yeah, because in the face of utter stupidity, it always works out so well, to instead of improve … you know education … just dumb everything down to utter-moron-level.

*Picard facepalm*

At May 2, 2013 at 9:13 PM , Blogger Evi1M4chine said...

testable ≠ tested.

A hypothesis becomes a theory by having its predictions observed… usually people draw a limit to how reliable (e.g. statistically) and trustworthy those observations have to be, before they rely on them to generally predict the future.

Because that’s what it’s all about: Predicting the future. (Grown out of the needs that stem from natural selection.)

At May 2, 2013 at 10:44 PM , Blogger Matt2884 said...

A theory is a hypothesis that has had it's predictions tested. Whether or not it is a successful theory depends on how it's predictions stand up to experiment.

At May 2, 2013 at 11:07 PM , Blogger TheMoreTheWonderGrew said...

@Evi1M4chine: I don't mean we dumb everything down, but that we don't let misunderstood terms hinder education. There are people who would understand better (and perhaps MUCH better) if a scientific theory were described using terms such as 'framework' (or some better term, probably).
Let's not let a term *hinder* education, but let's communicate better, rather than hold on obstinately to terms that become stumbling blocks.

At May 3, 2013 at 9:09 AM , Blogger Damien Hallsworth said...

The existence (or not) of objectivity is actually a philosophical question and is still debated. I wouldn't say its treatment in this article constitutes a "huge error" at all.

Intuitively science makes a lot more sense if you accept objectivity, and indeed many scientists operate with objectivist, positivist assumptions. They may be philosophically mistaken, but these assumptions usually don't validate their research findings because the scientific method doesn't require that objectivity be dispensed with as a belief; in fact quite the opposite.

This piece is obviously trying to sketch out a naive model of the scientific method for people who are starting out with their scientific understanding. Once the scientific method is understood, then one can begin to look at debates about the philosophy of science, and the epistemological issues therein.

At May 4, 2013 at 12:17 PM , Blogger RedZeshinX said...

Just wanted to mention a slight error in the article:

"The key difference between a hypothesis as used in day to day discord and a scientific hypothesis is that a scientific hypothesis is necessarily testable."

You use the word "discord", which means lack of concord or harmony between persons or things. I believe you mean "discourse", which is communication of thoughts by words and conversation.

At May 5, 2013 at 10:40 PM , Blogger Bob StClair said...

I would make one small change in the very clear diagram. Rather than say a hypothesis or theory is "True" I would say that it is "consistent with the known facts." Science is riddled with "true" hypotheses" which have later been shown to not be true at all. The phlogiston theory of combustion and the ether theory of space both were at one time considered true. They were consistent with the known facts at the time but were discarded when more facts brought forth more consistent theories. "True" sounds so final and unchangeable and leads to bad science.

At July 25, 2013 at 5:16 AM , Blogger Olya Olegovna said...

I think this is really a very nice post. Yevgen Dankanych

At August 2, 2013 at 1:10 PM , Blogger Honey Razwell said...

Holy crap. Please do NOT spread this nonsense.

There is NO hierarchy whatsoever between hypotheses, theories and laws. None. They are all different and serve different roles. They differ in BREADTH, NOT level of support.

There is NOT ANYTHING that makes a law " more true " than a theory! Laws, in science, CAN be wrong. They are NOT immutable. In fact, laws can be changed just as easily as theories with new evidence, realization of past mistakes or new gained perspectives.

Hypotheses do NOT become theories. Theories do NOT become laws. This can NEVER happen. One can NEVER grow into another.

Hearing people BUTCHER the meaning of these terms makes me barf in my mouth a bit. It is an extremely common mistake on the Blogosphere.

At August 2, 2013 at 1:15 PM , Blogger Honey Razwell said...

Hypotheses are NOT guesses- educated OR otherwise! Hypotheses are NOT ideas NOR predictions.

They are explanations for a narrow range of phenomena and often have MULTIPLE levels of support. Hypotheses can be EXTREMELY COMPLEX. For example, a particular hypothesis about meteorological interactions or nuclear reactions can be so complex that they are best described in the form of a long mathematical equation OR a computer program!In such cases, this may be called a model.

At August 2, 2013 at 2:25 PM , Blogger Daniel Kroner said...

Who are you replying to?

If it is to the article in general it is pretty clear that you didn't actually read it.

At August 2, 2013 at 2:53 PM , Blogger Honey Razwell said...

There is NO such thing as a singular method that all scientists follow or must follow. Scientists use literally THOUSANDS of very different methods in the various fields of science.

What we all learned in 6th grade- the rigid step by step singular "method" is WRONG. Little, if any, science is actually conducted this way.

"The Scientific method" is only an IDIOMATIC expression. It was NEVER meant to be taken literally.

Science circles back on itself. The silly chart above resembles the standard 7th grade nonsense.

It is a very inaccurate representation of how science is done in the real world. Experimentasl science is NOT "more rigorous" than non- experimental.

Astronomers, for instance, do NOT use the nonsense above that is similar to the 7th grade posters you will find. These posters describing "The Scientific Method" are erroneous.

"The Scientific Method" is an INSULT to all researchers past and present. No such thing exists.

At August 2, 2013 at 2:56 PM , Blogger Honey Razwell said...

You really need to educate yourself. There is NO such thing as a singular method that all scientists follow. It is a TOTAL MYTH. And it is a travesty and an insult because it ERRONEOUSLY makes science appear MUCH easier than it is. Only layman spread this nonsense.

You can start by typing this into Google : "The Scientific Method vs REAL Science"

it is SO SAD that kids are being taught incorrect information.


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